Use unicast IP address when sending unicast service reply

Use unicast IP address when sending unicast service reply

For each protocol (IPv4 and IPv6) we have two interfaces (sockets): one
for unicast and one for multicast. If we noticed CLASS_UNICAST in the
multicast query we were switching to unicast interface for sending
reply.

The problem was not passing destination IP address. It was resulting in
sending packet to multicast IP using unicast interface. As we don't
set IP_MULTICAST_TTL / IPV6_MULTICAST_HOPS for unicast ones TTL was 1
and packets were ignored.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>